1. Field of the Invention
The present invention relates to a vehicle control technique featuring multiple sensors, and more particularly to a control technique performed when some of the sensors have developed a fault.
2. Description of the Related Art
Two sensors for providing redundant control inputs are sometimes used in order to enhance the reliability of a control system. When the two sensors operate normally, the control inputs obtained therefrom are substantially equal to each other. However, the two control inputs differ greatly from each other when either sensor develops a fault. An important question is how to perform control in such cases.
JPA 9-191501 describes a technique in which control is continued using only one accelerator sensor when one of the two accelerator sensors in an electric vehicle exceeds the upper or lower limit of a normal output range. It is disclosed that when this happens, abrupt variations in torque are limited by a method in which the torque command value presented to a motor control circuit is temporarily delayed or the torque command value is increased substantially rectilinearly.
Such direct control of abrupt variations in torque makes the driver uncomfortable because the resulting torque variations are markedly different from those experienced during normal driving. A need has therefore existed for a technique that would allow a vehicle to remain substantially as maneuverable as during a normal operation even when some accelerator sensors have developed a fault.
Accordingly, an object of the present invention is to provide a novel technique for allowing a vehicle to be continuously controlled even when some accelerator sensor has developed a fault.
In order to attain the above and related objects of the present invention, there is provided a control device for controlling a vehicle using first and second accelerator sensors configured to provide an accelerator control input. The control device comprises a fault detector configured to detect that one of the first and second accelerator sensors has developed a fault; and an accelerator control input setting section configured to determine the accelerator control input using an output of a normal sensor other than a faulty sensor when the faulty sensor has been detected by the fault detector. The accelerator control input setting section divides a full range of output signal levels of the normal sensor into a plurality of regions including an opening region in which the accelerator control input increases at a first rate of change, and a closing region in which the accelerator control input decreases at a second rate of change, and determines a change in the accelerator control input depending on which of the plurality of regions contains the output signal level of the normal sensor.
In a preferred embodiment, the fault detector detects the faulty sensor by analyzing variation patterns of outputs of the first and second accelerator sensors when the outputs of the first and second accelerator sensors remain within respective normal output ranges thereof.
The present invention can be realized as a variety of embodiments. Examples include vehicle control devices and methods, vehicles provided with such control devices, computer programs for executing the functions of such control devices and methods, recording media for storing such computer programs, and data signals embodied in a carrier wave including such computer programs.